In recent years, photoelectric elements designed to convert light into electricity or electricity into light have been used as, for example, power generation devices (photoelectric conversion elements) by photoelectric conversion, such as a photovoltaic cell and a solar cell, light-emitting devices such as an organic EL device, optical display devices such as an electrochromic display device and electronic paper, and sensor devices designed to sense, for example, temperature and light.
The photoelectric element includes an electron transport layer, which is required to have high electron transport properties. With respect to the electron transport layer, an area of a reaction interface as the interface on which charge separation or charge coupling occurs, is an important element.
For example, Patent literature 1 discloses a semiconductor for a photoelectric conversion material including a semiconductor such as titanium oxide adsorbing a dye and a conductive material such as tin oxide. The semiconductor for a photoelectric conversion material is produced by applying a mixture of a semiconductor dispersion liquid and a conductive material dispersion liquid in an appropriate ratio onto a substrate coated with a transparent conductive film and further mixing a spectral sensitizing dye in the film including the mixture of the semiconductor and the conductive material. In the film obtained as above, the conductive material particles are homogeneously distributed in the semiconductor particles. Patent literature 1 also discloses a chemical cell that includes an electrode obtained by such a method of forming a photoelectric conversion material film on a transparent substrate coated with a transparent conductive film, a counter electrode that includes a substrate such as a glass substrate with a conductive film including, for example, platinum, and an electrolyte filled between the electrodes. The chemical cell works as below according to the description in Patent literature 1. Applying sunlight to the semiconductor for a photoelectric conversion material causes the sensitizing dye to absorb light to be excited. Electrons generated by the excitation move to the semiconductor, then pass through the transparent electrode and a load, and reach the counter electrode. The electrons transferred to the counter electrode reduce an oxidation-reduction system in the electrolyte. Meanwhile, the spectral sensitizing dye, from which electrons move to the semiconductor, is in an oxidation state and the oxidized form is reduced by the oxidation-reduction system in the electrolyte to return to the original form. Electrons continuously flow in this manner.
However, by the technique described in Patent literature 1, it is supposed that electrons excited by incident light are trapped by the conductive material having a high electric conductivity during the transfer of electrons in the semiconductor for a photoelectric conversion material including the semiconductor such as titanium oxide adsorbing a dye and the conductive material such as tin oxide, and this interferes with the electron transfer. On this account, the technique described in Patent literature 1 should not improve conversion efficiency.